I feel like your time would be better spent writing rather than doing these "sweeps". Put an address in the books so people can find legit copies of the for-pay story, and then don't worry about it; don't bother playing the piracy whack-a-mole game, it'll tax your sanity and you'll end up with exactly zero extra sales (and if it's not about the sales, then who cares?).

Good advice. I found my free book at a site that was listing it for $64.

If they're not selling it, and haven't stripped any copyright and other info out of the book, I'd suggest you provide them with alternate, non smashwords copies and ask them to include a link to your wesite or to the smashwords versions.

Really, the problem with most authors is getting publicity. Frankly, I'd consider this free publicity. In fact, I vaguly recall a graphic novel authore that increased his sales when he found his work scanned and posted on 4chan. Instead of trying to get it remove, he went online and provided higher quality versions and asked that anyone who liked it, please buy a copy.